Polymeric foam pads are typically used as a carpet underlayment to act as a cushion that improves the resiliency and comfort of the carpet. Historically, these foam pads have been made of low cost polyurethane foam “rebond” that is produced by bonding recycled foam scraps using isocyanate as binder to bond the foam pieces together. While being of low cost, polyurethane “rebond” has its disadvantages. For example, the thickness of “rebond” typically varies considerably, which results in inconsistent performance. In addition, because it is made of recycled foam materials, it can contain foam that has been exposed to people or animals or it can contain other contaminants, such as rubber crumb, which can be environmentally undesirable.
As a result, efforts have been made to produce polyurethane foam carpet underlayments using virgin materials. In some cases, these sheets are made by a polyurethane froth process in which the polyisocyanate and isocyanate-reactive ingredients are combined in a special mixer and allowed to froth to form a foam which is then formed into a sheet. This process has typically been used, however, only to produce higher density foams (usually from 10 to 20 lb/ft3 as compared to typical foam densities of 5 to 10 lb/ft3 for rebond) and is only used for producing carpet underlayments for use in specialty, high traffic area, applications, at least in part due to higher material costs due to the higher density.
Efforts have also been made to produce polyurethane foam carpet underlayments using virgin materials by a continuous process using a conveyor system in which the polyurethane foam is formed between two facing materials to form a sandwich structure. Examples of such processes are described in U.S. Pat. Nos. 5,531,849 and 5,798,064. A disadvantage of the processes developed to date, however, is that they have not been efficient enough to produce polyurethane foam carpet underlayments using virgin materials that are cost competitive with “rebond”.
As a result, it would be desirable to provide a continuous process to produce polyurethane foam carpet underlayments using virgin materials that is sufficiently efficient to be cost competitive with rebond, while providing a product with significantly more consistent thickness (gauge) control relative to rebond. Moreover, it would be desirable to provide such a process that does not require the use of an oven, and the capital and operating costs associated therewith, to cure the polyurethane to produce such an underlayment.
The present invention was made in view of the foregoing desire.